Mold-casting structure and improvement method for grounding of the same

ABSTRACT

A mold-casting structure comprises at least one dishing and a plurality of micro-protrusions. The dishing(s) formed on the surface of a mold-casting body, the plurality of micro-protrusions sticking out of the surface of the dishing, and the tops of the micro-protrusions constitute on a plane, so that the grounding issue of the circuitry embedded in the mold-casting structure caused by the dishing can be resolved. The dishing can be verified by daubing paint and scrapping thereafter, the location of remaining paint is deemed the dishing. Moreover, a three-dimensional measurement instrument can be employed for more precise measurement. The micro-protrusions can be formed on the dishing by mechanical processing or electric discharge machining (EDM). Alternatively, a mold with a structure matching the micro-protrusions can be formed first, and consequently the micro-protrusions are formed directly by mold-filling, which is more suitable for mass production.

BACKGROUND OF THE INVENTION

(A) Field of the Invention The present invention is related to a mold-casting structure and the relevant electrical grounding method thereof. In view of the superior grounding efficiency of the mold-casting structure of the present invention, EMI (Electromagnetic Interference) can be prevented effectively.

(B) Description of Related Art

The satellite television systems employ a dish antenna to collect satellite signals, and the signals are then reflected to low noise block down converters (LNB) equipped at the focus of the dish antenna for amplifying the signals and reducing its frequency down to around 1 GHz, i.e., the radio signals are transformed to an intermediate frequency. The adjusted signals are transmitted to an indoor television channel selector via a cable to select the signals of a desired channel, and the selected signals are then amplified, modulated, and then converted into video and audio signals for television viewing.

Noise minimization is crucial to maintaining the quality of microwave telecommunication. LNB components essentially comprise a housing, horns, and a connector base. After an LNB is released from a mold, some dishings occur on the surface of the component due to the shrinkage of the material, e.g., aluminum alloy or plastic, while cooling.

These dishings often occur at the positions having protrusions in the opposite side, e.g., a rib for heat dissipation or a thick portion. FIG. 1 illustrates an LNB housing 11 with protrusions 12 on the bottom surface. When the LNB is released from a mold, dishings 13 occur at the opposite surface of the protrusions 12. As a result, the grounding quality of a printed circuit board established inside the LNB housing 11 will become worse.

The dishings cause errors of the dimensions to the original design, thus the effect of EMI prevention is inferior due to bad grounding quality. Consequently, the circuitry secured therein may need to be modulated, or have the dishings deposited with tin foil or filled in with conductive material to improve the grounding quality. As a result, the time and cost of the process will increase and the reliability will be difficult to control.

Therefore, if the dishings on the mold-casting structure occurring after mold-release can be repaired to increase the grounding efficiency, the EMI will be diminished effectively, and thus the signals will be transmitted with high quality.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a mold-casting structure with high grounding efficiency, which can resolve the problem of inferior electrical conduction due to dishings occurring on the mold-casting structure after the mold-casting structure was released from the mold, and so as to avoid EMI effectively.

To achieve the above objective, the present invention discloses a mold-casting structure. The mold-casting structure comprises at least one dishing and a plurality of micro-protrusions. The at least one dishing formed on the surface of a mold-casting body, the plurality of micro-protrusions sticking out of the surface of the dishing, and the tops of the micro-protrusions constitute a plane, so that the grounding issue of a circuitry designed in the mold-casting structure caused by the dishing can be resolved.

The dishing can be verified by spraying paint and scraping the paint with a scraper along a plane afterwards, the locations that the paint remains are verified as dishings. In addition, a three-dimensional measurement instrument can also be used for more precisely measuring the contours and dimensions of the dishing.

The micro-protrusions can be formed on the dishing by mechanical processing or electric discharge machining (EDM). Furthermore, a concave-convex structure matching the micro-protrusions can be formed on the mold. Accordingly, the micro-protrusions can be fabricated by casting directly, and therefore it is more suitable for mass production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates dishings on an LNB housing; and

FIGS. 2 through 4 illustrate an LNB mold-casting structure and the relevant grounding improvement method in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 2, an LNB structure 20 for microwave telecommunication comprises a housing 22, two horns 24, and two connector bases 26, where the housing 22, with the locations corresponding to the horns 24, is provided with two through holes shaped like semi-circles for the connection of signal cables to the horns 24. Only one horn 24 can be seen in FIG. 2, the other one is behind the housing 22 and thus not shown.

FIG. 3 illustrates the bottom view of the housing 22. After the LNB structure 20 is released from a mold and cooled down, a painting material such as a traditional paint, an ink marker or a red lead paint is daubed on the bottom surface 22 a of the housing 22, and then scraped by a tool such as a scraper along a plane that is substantially equivalent to the bottom surface 22 a but without protrusions or dishings. Accordingly, the paint on the protruded portions will be removed, so that the locations with remaining paint can be deemed dishings 30. In this embodiment, the dishings 30 are closed to the through holes 28, i.e., the dishings 30 are closed to the opposite side of the horns 24, the phenomenon reflects material shrinkage.

After the locations of dishings 30 are verified, a three-dimensional measurement instrument can also be used to more precisely measure the dishings 30, so as to obtain data such as the depths and contours of the dishings 30. Then, a plurality of micro-protrusions 32 are formed on the dishings 30 on the bottom surface 22 a by various mechanical processes (for example, pin hammer) or electric discharge machining. The tops of the micro-protrusions 32 can essentially constitute a plane, so as to resolve the grounding problem.

As shown in FIG. 4, a convex-concave structure 42 matching the micro-protrusions 32 can be formed on a mold 40 for manufacturing the LNB structure 20, so that the micro-protrusions 32 are formed naturally after the LNB structure 20 is released from the mold 40. The micro-protrusions 32 make up the dishings 30, so that the inferior grounding issue due to inferior electrical conduction will be resolved.

In this embodiment, the LNB structure 20 can be made of aluminum alloy or plastic. The diameter of a micro-protrusion 32 is between 0.01 and 5 mm, and the height thereof depends on the depth of the dishing 30. The distance between neighboring micro-protrusions 32 is between 0.01 and 0.5 mm.

The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be devised by those skilled in the art without departing from the scope of the following claims. 

1. A mold-casting structure, comprising: at least one dishing formed on a surface of a mold-casting body; and a plurality of micro-protrusions formed on the dishing, and the tops of the plurality of micro-protrusions constitute a plane; whereby the inferior grounding of the circuitry secured on the mold-casting structure due to the dishing can be avoided.
 2. The mold-casting structure of claim 1, which is made of aluminum alloy or plastic.
 3. The mold-casting structure of claim 1, wherein the distance between neighboring micro-protrusions is between 0.01 and 5 mm.
 4. The mold-casting structure of claim 1, wherein the diameter of the micro-protrusion is between 0.01 and 5 mm.
 5. The mold-casting structure of claim 1, which is applied to a microwave telecommunication apparatus.
 6. The mold-casting structure of claim 1, which is applied to a low noise block down converter (LNB).
 7. An improved method for grounding of a mold-casting structure, comprising: verifying a location of at least one dishing on the mold-casting structure; and forming micro-protrusions on the at least one dishing.
 8. The mold-casting structure of claim 7, wherein the dishing is verified by a three-dimensional measurement instrument.
 9. The mold-casting structure of claim 7, wherein the verification for the location of the dishing comprises the steps of: daubing paint on a surface of the mold-casting structure; and scraping the surface along a plane, and the location of the remaining paint being deemed the dishing.
 10. The mold-casting structure of claim 7, wherein the micro-protrusions are formed on the surface of the dishing by mechanical processing or electric discharge machining.
 11. The mold-casting structure of claim 7, wherein the micro-protrusions are formed on the surface of the dishing by a pin hammer.
 12. The mold-casting structure of claim 7, wherein the micro-protrusions are molded by a mold with a concave-convex structure matching the micro-protrusions. 